Originally Posted by
Mercen-X
One of two ways: if you did every last sidequest, then presumably you have to talk to Tifa in the sewers instead of Aerith.
Otherwise just avoid doing Aerith's sidequests.
I've tested this. Here's what I did: I completed the game on Hard Mode doing all of the sidequests in order to collect every manuscript. Obviously, this includes the sidequests in Chapter 3 (for Tifa) and Chapter 8 (for Aerith). During this run, I spoke to Tifa first in the Sewers. In Chapter 14, Tifa met me the Garden. After completing the game, I went back to Chapter 10 in the Sewers and spoke to Aerith instead of Tifa and completed the Chapter. I returned to Chapter 14. It was Aerith in the Garden. Next, I played through Chapter 8 and called it quits right after the fight with Rude (meaning I went into Aerith's house) then completed the chapter. Chapter 14 showed Tifa this time ('cause this playthrough still registered Tifa's sidequests). Finally, I replayed chapter 3 and skipped the sidequests (well you have to do one, optimally Chadley's as he's right there. Then you have to save Johnny otherwise you can't get back to the bar. Funny enough, you can avoid Johnny sidenote if you do all of the other sidequests.) Anyway, on my final return to Chapter 14, with no sidequests cleared for Tifa or Aerith, it was Barret in the Garden.
BOO.-.-.YAH